Thirty-years assessment of size-fractionated particle mass concentrations in a polluted urban area and its implications for the regulatory framework

Among the different atmospheric pollutants, since the late 70s, great attention has been devoted to Particulate Matter (PM). Considering a database of 30 years of size-fractionated PM10 measurements, we have observed the positive impact of the gradual introduction of different air quality regulations. In fact both PM10 and PM2.5 and PM1 absolute concentration levels have been reduced during this period. In particular the mean recorded values are: 63 μg/m3 (PM10), 38 μg/m3 (PM2.5) and 22 μg/m3 (PM1) in year 1980. We recorded a mean value of 59 μg/m3 (PM10), 41 μg/m3 (PM2.5) and 32 μg/m3 (PM1) in year 2000. Finally we measured a mean value of 45 μg/m3 (PM10), 34 μg/m3 (PM2.5) and 29 μg/m3 (PM1) in year 2011. Nevertheless, major adverse health effects are still recorded. Even if a complete toxicological description of PM impact is still in progress and several aspects related to the chemical and mutagenic effects of PM should be deeper investigated, we suggest that the relative size concentrations are also of paramount importance. In fact, even if the absolute concentrations of the three inhalable PM fractions decreased, finer fractions relative concentrations have increased in the period 1980-2010. In particular, the relative values of PM2.5 and PM1 are: 61% (PM2.5) and 35% (PM1) in year 1980; 70% (PM2.5) and 54% (PM1) in year 2000; 75% (PM2.5) and 65% (PM1) in year 2011. Results suggest that the introduction of new limitations to sub-micron particles (PM1) emissions is advisable. Furthermore, possible improvement of air quality management might derive from differentiated local/regional limitations, depending on the characteristics of the exposed population and on the local meteorological and geographical characteristics of the sites showing higher aerosol pollution levels.